In the start if the film the audience discovers that Leonard Shelby, has made substantial progress in his circumstance due to his intelligence since the accident, his wife being brutally raped and murdered by two men where he was struck on the head causing the amnesia. He has formulated a way each day to where he can live with progress in mind instead of waking up in square one. He uses a direct system of leaving purposeful notes to where he will go, who he will encounter, and what he has to do in order to find the man who raped and killed his wife. He does this not only by permanently marking his bodies with tattoos but leaving a trail of photographs and notes which he keeps with him to find every few minutes. His goal is simple: revenge. However as he soon realizes at the beginning of the film he has met a few "friends" along the way that have either tried to help him, or lead him astray in his mission. For which reason? He cannot seem to remember. He encounters Teddy and learns that he has detailed great parts of his life ad condition and purpose to him, yet each time he encounters Teddy he cannot remember meeting him except through a photo he carries around. He also has much contact with a lady named Natalie, whom also knows much about him, yet his memory of her is absent. The uncertainty reduction theory in Shelby's life is beyond twisted. People feel more certain around him, because they have had such events as information seeking, and verbal communication, yet Shelby has to develop new ways to reduce uncertainty through mementos because he cannot remember any of these interactions. Verbal communication, information seeking and other ways of uncertainty reduction do not work in Shelby's situation. As he states in the movie, he has to rely on his handwriting, his note taking, and his ability to not be manipulated by his so- called "friends" in his search to find his wife's killer, but whether they work or not? That too he cannot remember.
Berger's "Uncertainty Reduction" theory does not seem to apply for Shelby, While it seems to correlate with Teddy and Natalie each time the interact with Shelby, his inability to remember who they are or how they know him inhibit his ability to become less uncertain in his situations with them. I believe this inability of Shelby shows the truth that lies behind this theory even more. Humans have constant interaction with each other on a daily basis, through occupations, school, friendships, etc. And through each relationship or interaction with another human the theory of "Uncertainty Reduction" was used to an extent, whether consciously or subconsciously. It is very difficult for humans to interact with each other especially in a needed progressive situation, as like a job, if a great level of uncertainty lies between co-workers, clients, etc. While each and every human utilizes techniques to reduce uncertainty between other humans, over all this helps better understand their own interpersonal world. We understand ourselves better when we share information with another being. We understand our personality better when we interact non verbally with a stranger. We discover what we want out of an interaction through information seeking and self-discolsure. We use this "Uncertainty Reduction" theory everyday in every situation and interaction we have with the world around us. The more we can reduce uncertainty the better we will be able to live and progress in our lives. I believe it is a direct correlation between the two. "Memento" gives us a peek into how difficult it would be to not be able to every reduce uncertainty in our lives or interaction no matter how hard we tried, and I do not believe any human would desire to live with the difficulties Leonard Shelby has to deal with and overcome.